Chapter 31. The Control of Gene Expression in Prokaryotes

Question 1

In lactose metabolism, an essential enzyme that hydrolyzes lactose into galactose and glucose.

Answer 1

β-galactosidase

Question 2

The repression by glucose of catabolic enzymes required for the catabolism of carbohydrates other than glucose.

Answer 2

catabolite repression

Question 3

A small molecule that binds to a repressor protein; the corepressor-repressor complex then binds to the operator DNA of a particular operon to inhibit transcription.

Answer 3

corepressor

Question 4

The cAMP response protein; when bound to cAMP, ____ binds to an inverted repeated of the lac operon, near position -61 relative to the start site of transcription, to stimulate transcription.

Answer 4

catabolite activator protein (CAP)

Question 5

A signal molecule released by bacteria that participate in quorum sensing.

Answer 5

autoinducer

Question 6

In bacteria, a mechanism for transcriptional regulation in which a decrease in the rate of translation of an mRNA operon reduces the rate of transcription of that operon.

Answer 6

attenuation

Question 7

Specialized structures formed, often by quorum sensing, in which bacteria bind to each other and specific molecules that serve as scaffolds. Bacteria living in _____ resistant to the immune response of the host as well as to antibiotics.

Answer 7

biofilm

Question 8

A small protein that binds to the same sites as the λ repressor does, but with a different order of affinity for the three sites in the right operator.

Answer 8

CRO

Question 9

The regulatory sequence of the lac operon to which the lac repessor binds, and thus inhibits transcription of the operon. When bound to lactose, the repressor leaves the operator and transcription occurs.

Answer 9

lac operator

Question 10

The regulator protein that binds to the operator site of the lac operon and thereby inhibits expression of the structural genes of the operon; inhibition is relieved when the repressor protein binds allolactose, an inducer of the lac operon.

Answer 10

lac repressor

Question 11

A small molecule that binds to a repressor and alters its interaction with an operator.

Answer 11

inducer

Question 12

A protein that binds to an operator sequence and inhibits the transcription of the structural genes in the operon.

Answer 12

repressor

Question 13

A model of prokaryotic gene regulation that consists of an operator sequence and its associated structural genes.

Answer 13

operon model

Question 14

An inducer of the lac operon; ITPG binds to the lac repressor and reduces the repressor’s affinity for the operator DNA, which permits transcription to take place.

Answer 14

isopropylthiogalactoside (IPTG)

Question 15

A protein regulator of the pur operon, which encodes genes taking part in purine biosynthesis; the pur repressor binds to operator DNA only when bound to a small molecule (guanine or hypoxanthin) called a corepressor.

Answer 15

pur repressor

Question 16

A type of social interaction in bacteria, facilitated by the release of autoinducers by the bacteria, that can change the patterns of gene expression within the cells.

Answer 16

quorum sensing

Question 17

A regulatory DNA sequence that is part of the operon model.

Answer 17

operator site

Question 18

A recurring motif found in many DNA-binding proteins, in which two α-helical segments are linked by a short hairpin turn; the two segments are 34 Å apart, which allows them to fit into adjoining major grooves in DNA.

Answer 18

helix-turn-helix motif

Question 19

Sometimes known as λ cI protein, this protein blocks, either directly or indirectly, the transcription of almost all genes encoded by the virus. It consists of an amino-terminal DNA-binding domain and a carboxyl-terminal domain that participates in protein oligomerization.

Answer 19

λ repressor